Best of my recollection from S&W factory revolver class is that it will drive out either way. I tend to drive pins out from left to right just on general principle. Other than remembering to actually remove the pin it's just the same as anything else. Barrels are usually "cinched down" about 1/8 or 1/10 of a turn. They often will not reseat properly unless you take the shoulder down a full turn so they can be recinched. Some people report good success with a slightly stiff fit and loctite on the barrel threads.

You might want to wait for a response from someone who has done it recently before you drive out that pin, but I am pretty sure.

When changing a revolver barrel you'll need some fairly expensive tools to do it.

Among them is a special frame wrench with inserts to fit THAT specific model and brand, a lathe to turn down the barrel shoulder, a barrel vise, a special tool that works down the bore to re-cut the barrel/cylinder gap (you don't do that with a file), and another special tool set that works down the bore to re-cut the forcing cone, lap it smooth, and a special plug gage to gage the cone to insure its the right diameter at the throat.

How to ruin a nice gun:
Use a hammer handle through the frame to twist the frame off.
Use a file to file the barrel to set barrel/cylinder gap.
Ignore the forcing cone entirely.

Then wonder why the gun doesn't shoot as well as it did, or why it suddenly has problems.
Re-barreling a revolver is a major pistolsmithing operation.

I bought this revolver, a S&W 66-1, new in the very early 80s, perhaps 1980 or '81. The younger guys won't recall this, but you geezers like me remember that in those days S&W Stainless revolvers in any guise were hard, hard to come by. The police were buying them faster than Smith could make them.

I finally found this one and I bought it although I really wanted a 4" model. I don't recall the retail price, I think in the high 200s. I know I paid substantially more than that because of the shortage. There were no internet auction sites like we take for granted today, but the dealers still knew what was hot and on those guns they jacked the price. Pure supply and demand. This old gun has served me well over the past 30 years, many many many rounds through it.

Still, I've always wanted a 4" 66, though I now have plenty of other Smith revolvers. So I've always kept my eye out for a 4" barrel with the idea of converting the old 6". And finally found one a year or so ago.

As you may imagine, I was intimdated by Mr. Farriswheels reply (see above). I thought it over, considered his advice, and decided to proceed anyway, even though I do not have the tools he requires.

Removing the barrel was done with a home made wrench. This was two blocks of wood whittled to more or less cradle the front of the frame, along with a pair to cradle the barrel in the vise.

I clamped the barrel in a solidly mounted vise. I had put the crane back in the gun to fill the hole in the front of the frame and re-installed the side plate. I was trying to keep everything as solid as possible. I used rubber cement to attach the frame blocks (I really needed have 3 hands). Then I put a very large clamp over the blocks, twisted it and the frame / 6" barrel separated without any fuss and no flex damage I could measure. Everything is quite smooth with no sign of any binding or misalignment or stiffness that I could find.

Installing the very slightlty used 4" barrel, I found it would not draw up far enough to center either the grooves or the front sight. Hmmmm.... I carefully, slowly filed the circumference of the barrel shoulder back until it would stop at the same place as the old barrel, and showed good contact with the frame around the circumference. I used a Brownells 1911 square barrel fitting file for this. It is an extremely fine cut. Then I cinched the barrel in place the same way I removed the old barrel, aligned the sight to vertical by eye. I cannot tell any off-center.

The B/C gap was too small, but it always has been on this gun. Still, it went from .004" on the 6", down to .002" on the 4". This was expected, measuring the old v. new barrels showed about .002" extra on the 4" barrel. I made a .003" shim for the end of the crane which gave a .004-.005 gap and I'm satisfied. I also took the opportunity to fix a longstanding problem with this gun. The frame cut for the cylinder ratchet was not cut to full depth just under hand slot, I've no idea how this could happen, but no doubt it did. Very often this high area would interfere with the cylinder rotation when the bolts on the star would rub against that high spot. I very very slowly & carefully ground it flush with the dreaded Dremmel, a very fine small stone, and low speed.

So the big question, how does it shoot. In my tests it shoots better than it did with the original barrel. See the photos. But in all honesty, I was never satisfied with the gun with a 6" barrel so it's for sure possible I never tried as hard with it as I did today. Anyhow, it shoots very well for a stock, untuned S&W J-Frame 4". The rear sight goes point of aim when nearly dead centered latterally, so I think everything is aligned right. No sign of spitting through the gap.

Given Mr. Farriswheels comments, I'm still not sure I would recommend the unskilled attempt this. I have not a lot of revolver experience but I do have some, and alot more on 1911 type pistols - I build my own from parts. So I'm not a neophyte at this. And no one with any sense would try to make a living doing it this way. It probably took me 4x - 5x as long as a pro would need. Actually the whole process, everything described plus disassembly / re-assembly took 4-5 hours. It's a hobby, not a vocation.

Pics - 1st the gun with the new barrel, old barrel also shown, and a 12 shot group at 27 yards, measured, handheld from a rest. 7.5gr Unique / 140 Rem. JHP. These clock around 1100fps, warm but not full power.

Plates shot with this gun. The upper groups were done with .38 spl.
4.3gr BE / 140 Rem JHP (all shots used this bullet), range 78 yards, handheld from a rest. Avg. 890fps. Lower plates with the .357 as above. Plates are around 14" wide.

It nice to have your own range. (Some maintenance is due, will be done soon).

I bought this revolver, a S&W 66-1, new in the very early 80s, perhaps 1980 or '81. The younger guys won't recall this, but you geezers like me remember that in those days S&W Stainless revolvers in any guise were hard, hard to come by. The police were buying them faster than Smith could make them.

I finally found this one and I bought it although I really wanted a 4" model. I don't recall the retail price, I think in the high 200s. I know I paid substantially more than that because of the shortage. There were no internet auction sites like we take for granted today, but the dealers still knew what was hot and on those guns they jacked the price. Pure supply and demand. This old gun has served me well over the past 30 years, many many many rounds through it.

Still, I've always wanted a 4" 66, though I now have plenty of other Smith revolvers. So I've always kept my eye out for a 4" barrel with the idea of converting the old 6". And finally found one a year or so ago.

As you may imagine, I was intimdated by Mr. Farriswheels reply (see above). I thought it over, considered his advice, and decided to proceed anyway, even though I do not have the tools he requires.

Removing the barrel was done with a home made wrench. This was two blocks of wood whittled to more or less cradle the front of the frame, along with a pair to cradle the barrel in the vise.

I clamped the barrel in a solidly mounted vise. I had put the crane back in the gun to fill the hole in the front of the frame and re-installed the side plate. I was trying to keep everything as solid as possible. I used rubber cement to attach the frame blocks (I really needed have 3 hands). Then I put a very large clamp over the blocks, twisted it and the frame / 6" barrel separated without any fuss and no flex damage I could measure. Everything is quite smooth with no sign of any binding or misalignment or stiffness that I could find.

Installing the very slightlty used 4" barrel, I found it would not draw up far enough to center either the grooves or the front sight. Hmmmm.... I carefully, slowly filed the circumference of the barrel shoulder back until it would stop at the same place as the old barrel, and showed good contact with the frame around the circumference. I used a Brownells 1911 square barrel fitting file for this. It is an extremely fine cut. Then I cinched the barrel in place the same way I removed the old barrel, aligned the sight to vertical by eye. I cannot tell any off-center.

The B/C gap was too small, but it always has been on this gun. Still, it went from .004" on the 6", down to .002" on the 4". This was expected, measuring the old v. new barrels showed about .002" extra on the 4" barrel. I made a .003" shim for the end of the crane which gave a .004-.005 gap and I'm satisfied. I also took the opportunity to fix a longstanding problem with this gun. The frame cut for the cylinder ratchet was not cut to full depth just under hand slot, I've no idea how this could happen, but no doubt it did. Very often this high area would interfere with the cylinder rotation when the bolts on the star would rub against that high spot. I very very slowly & carefully ground it flush with the dreaded Dremmel, a very fine small stone, and low speed.

So the big question, how does it shoot. In my tests it shoots better than it did with the original barrel. See the photos. But in all honesty, I was never satisfied with the gun with a 6" barrel so it's for sure possible I never tried as hard with it as I did today. Anyhow, it shoots very well for a stock, untuned S&W J-Frame 4". The rear sight goes point of aim when nearly dead centered latterally, so I think everything is aligned right. No sign of spitting through the gap.

Given Mr. Farriswheels comments, I'm still not sure I would recommend the unskilled attempt this. I have not a lot of revolver experience but I do have some, and alot more on 1911 type pistols - I build my own from parts. So I'm not a neophyte at this. And no one with any sense would try to make a living doing it this way. It probably took me 4x - 5x as long as a pro would need. Actually the whole process, everything described plus disassembly / re-assembly took 4-5 hours. It's a hobby, not a vocation.

Pics - 1st the gun with the new barrel, old barrel also shown, and a 12 shot group at 27 yards, measured, handheld from a rest. 7.5gr Unique / 140 Rem. JHP. These clock around 1100fps, warm but not full power.

Plates shot with this gun. The upper groups were done with .38 spl.
4.3gr BE / 140 Rem JHP (all shots used this bullet), range 78 yards, handheld from a rest. Avg. 890fps. Lower plates with the .357 as above. Plates are around 14" wide.

It nice to have your own range. (Some maintenance is due, will be done soon).

Some stainless Smiths.

You are just showing off to make us drool. How cruel. Beautiful set of firearms.

While in general, dfariswheel is right on the money, there are a select few who can do an excellent job with simple hand tools - you seem to be one of them.

I am a collector of vintage electric fans (mostly GE) from the early teens up to the 1940's and for the most part there are parts still available if you look very very hard. When my parents died, I inherited a Manning Bowman 10" fan that back in the day was a less expensive brand than GE and parts for them are very difficult (or impossible) to find. There is one Nylon drive gear that has a helical cut to it and deep pitch that broke and after looking all over for a year or so I decided to MAKE one by hand! I do not have a lathe or milling machine so the part was made 100% by hand using a Dremel, hand saws, a drill press, files, and sandpaper. I was amazed that when I finished and installed it, it actually works pretty well. The fan now oscillates (not quite as smoothly as when new) but it does work. All my friends told me I was nuts and I should just leave it as a "non-oscillating" fan - but not me! I suppose I did it as a "dare" as well, but I am glad I tried and was successful.

For one that is determined, has adequate skills, proper tools and most importantly UNDERSTANDS how it has to be, then nothing is impossible - even if it is sort of a crude method as compared to a Professional Gunsmith.
Good for you gbw!